1. Field of the Invention
The present invention relates to a battery pack including, in addition to a battery protection IC, a control IC for controlling the battery pack.
2. Description of the Related Art
A conventional battery pack is described. FIG. 5 is a block diagram illustrating the conventional battery pack.
A battery protection IC 91 controls N type FETs 93 and 94, respectively, based on a voltage of a battery 95. An overdischarge voltage indicating that the battery 95 is in an overdischarge state, an overcharge voltage indicating that the battery 95 is in an overcharge state, and a discharge overcurrent indicating that the battery 95 is in an overcurrent state during discharge are set therein in advance, and if the voltage of the battery 95 becomes equal to or lower than the overdischarge voltage, a voltage of a discharge control terminal DO is controlled to Low so that the N type FET 93 is turned OFF to stop the discharge from the battery 95. On the other hand, if the voltage of the battery 95 becomes equal to or higher than the overcharge voltage, a voltage of a charge control terminal CO is controlled to Low so that the N type FET 94 is turned OFF to stop the charge to the battery 95. Further, if a discharge current of the battery 95 becomes equal to or larger than the discharge overcurrent, the voltage of the discharge control terminal DO is controlled to Low so that the N type FET 93 is turned OFF to stop the discharge from the battery 95. A control IC 92 controls the battery protection IC 91 on a given occasion.
The battery protection IC 91 includes a terminal Din and a terminal Aout, which are for use in communication with the control IC 92. The control IC 92 includes a terminal Dout and a terminal Ain, which are for use in communication with the battery protection IC 91. The terminal Din and the terminal Dout are connected to each other, and the terminal Aout and the terminal Ain are connected to each other (see, for example, Japanese Patent Application Laid-open No. 2003-111284).
In the technology disclosed in Japanese Patent Application Laid-open No. 2003-111284, when the control IC 92 is controlled based on a state of the battery 95, the battery protection IC 91 detects the state of the battery 95 and sends a predetermined signal to the control IC 92 based on the detection result. In other words, in this case, the battery protection IC 91 requires the terminal Aout without exception. Accordingly, the number of terminals in the battery protection IC 91 is increased correspondingly.